The objectives of this project are to define the lesion(s) that occur during storage of platelets at predetermined temperatures and periods of time. The effect of storage on the integrity, vital functions and interrelations of platelet microtubule and microfilament system is undefined because the individual components of each system are at present only partially known. We propose to investigate the functional stability and interelationships of several platelet microstructures, i.e., membranes, microtubules, microfilaments, mitochondria and cytoplasmic proteins. Biochemical studies can define alteration of individual properties of each system. These alterations could result in morphological changes determined electronmicroscopically. The variations observed will be then correlated with functional changes determined in intact platelets: platelet aggregation, capacity of platelets to correct hemorrhagic or hematological deficiencies, initially with animal models, and survival and function of platelets treated with reagents to stabilize their microstructures. We believe that the identification of storage lesions will serve as indicator(s) for defining appropriate storage conditions that will permit optimal preservation of platelet function and survival in vivo.